"Behavioural despair" in rats and mice: strain differences and the effects of imipramine.

Rats and mice when forced to swim in a restricted space will rapidly cease attempts to escape and become immobile. Previous experiments have shown that immobility was selectively reduced by antidepressant agents. The present experiments show that important differences exist between strains in both the amount of immobility observed and the effects of imipramine. Strain differences should therefore be taken into account in attempts to replicate results from one laboratory to another.